Carbon dioxide fixation by Cp 2(η 3-allyl)Ti complexes generated from various dienes

Boosting CO2 Conversion with Terminal Alkynes by Molecular Architecture of Graphene Oxide-Supported Ag Nanoparticles

Since carbon dioxide (CO2) is an abundant, economical, nontoxic and environmentally benign C1 chemical reagent, fixation of carbon dioxide in organic molecules has recently become an attractive project in organic synthesis. An electrochemical method has contributed greatly to this area because it enables an efficient fixation of carbon dioxide in organic molecules even under atmospheric pressure of carbon dioxide when a reactive metal, such as magnesium or aluminum metal, is used as a sacrificial anode. There have been a number of reports on electrochemical fixation of carbon dioxide, and we have also reported synthesis of useful carboxylic acids by electrochemical carboxylation of various organic compounds. On the other hands, it is well known that fluorine-containing organic compounds have unique chemical and physical properties. The introduction of fluorine atoms into biologically-active compounds is also known to cause remarkable modification of their original activities. Therefore, considerable attention has been paid to efficient and selective preparation methods of organofluorine compounds. However, little attention has been paid to electrochemical carboxylation to afford fluorinated carboxylic acids.1-4 During the course of our continuous studies on the synthesis of useful carboxylic acids by electrochemical fixation of carbon dioxide,5 we recently found that electrochemical reduction of polyfluoroarenes in the presence of carbon dioxide resulted in a regioselective cleavage of a C-F bond of the phenyl ring followed by reaction with carbon dioxide to give the corresponding mono-carboxylated products, polyfluorobenzoic acids, in moderate to good yields.6 We report herein the results for synthesis of polyfluorobenzoic acids by regioselective electrochemical carboxylation of polyfluoroarenes.First, we screened reaction conditions for electrochemical carboxylation of hexafluorobenzene (1a) as a substrate. When constant current electrolysis of 1a was carried out in DMF using a one-compartment cell equipped with a Pt cathode and an Mg anode with 3 F/mol of electricity in the presence of carbon dioxide, reductive cleavage of a C-F bond on the phenyl ring followed by reaction with carbon dioxide took place to give pentafluorobenzoic acid (2a). After reaction conditions screening, 2a could be obtained in 73% 19F NMR yield by electrolysis of 1a at –40°C with 5 mA/cm2 of current density. After recrystallization with hexane and acetone, pentafluorobenzoic acid (2a) was obtained in 65% isolated yield as a pure product.We next investigated similar electrochemical carboxylations of several polyfluoroarenes, and the results are shown in Scheme. When pentafluorobenzene (1b) was subjected to the present electrochemical carboxylation under the same conditions for the reaction of 1a, C-F bond cleavage followed by carboxylation also took place efficiently to give 2,3,5,6-tetrafluorobenzoic acid (2b) in 78% 19F NMR yield and 66% isolated yield after recrystallization. It is noteworthy that C-F bond cleavage followed by carboxylation of 1b occurred at the C3 position of 1b predominantly to give 2b as a major product. Similar regioselective electrochemical carboxylation was also achieved when pentafluoroarenes 1c-f were used as substrates. Under the same conditions except for 1d, electrochemical carboxylation of 1c-f gave 4-substituted-2,3,5,6-tetrafluorobenzoic acids 2c-f in 61-84% 19F NMR yields and 49-76% isolated yields after recrystallization. It is also to note that C-F bond cleavage occurred at the para position of the substituents of Me-, AcO-, Me(RO)2C-, and MeS- in pentafluoroethylarenes 1c-f predominantly in all cases to give 4-substituted-2,3,5,6-tetrafluorobenzoic acids 2c-f as major products.<Scheme>Other results of electrochemical carboxylation of polyfluoroarenes and proposed reaction mechanism including regioselectivity of the carboxylation will be presented.

Electrochemical fixation of carbon dioxide in organic compounds with C–C bond formation yielding carboxylic acids is focused and reviewed in this chapter. Electrolysis of organic compounds in the presence of carbon dioxide results in efficient fixation of carbon dioxide in organic compounds with C–C bond formation to yield the corresponding carboxylic acids. When electrolysis is carried out in one-compartment electrochemical cell (undivided cell) using magnesium or aluminum as an anode material, efficient carboxylation can be achieved to give carboxylic acids in high yields. Electrochemical carboxylation is sometimes carried out in the presence of transition-metal catalyst, such as nickel, palladium, and their complexes, or electron transfer mediator, the use of which often results in drastic enhancement and control of chemo- and regioselectivity and efficiency of carbon dioxide fixation. Various organic compounds can be electrochemically carboxylated to give useful carboxylic acids. Some of them cannot be synthesized by conventional chemical fixation of carbon dioxide. One notable synthetic application of electrochemical fixation of carbon dioxide is synthesis of 2-arylpropanoic acids, nonsteroidal anti-inflammatory drugs (NSAIDs), and their useful precursors and derivatives. Electrochemical fixation of carbon dioxide also takes place by using supercritical carbon dioxide (scCO2), which can be realized under relatively moderate conditions (Tc = 31 °C, Pc = 7.5 MPa). By using acetonitrile as a cosolvent, efficient electrochemical fixation in scCO2 in organic compounds can be achieved and carboxylic acids including NSAIDs and their precursors can be obtained in high yields. In this chapter, these results are widely introduced with several representative examples.

Diarylation of N- and O-nucleophiles through a metal-free cascade reaction

In the past three decades, we have focused on the fixation of carbon dioxide by electrochemical method with a carbon-carbon bond forming reaction to yield carboxylic acid, so-called electrochemical carboxylation. Vinyl bromides and triflates, difluoroethylbenzenes, polyfluoroarenes, benzal diacetates, phenyl-substituted alkenes and enamides, and α-aminosulfones were found to be effective as substrates for electrochemical carboxylation. Phenylacetic acids and phenylpropanoic acids including non-steroidal anti-inflammatory agents and their fluorinated analogues, polyfluorobenzoic acids, mandel acetates, and α- and β-amino acids were successfully synthesized. Electrochemical double carboxylation of dibenzyl carbonates, reuse of carbon dioxide in benzyl carbonates for fixation of carbon dioxide (recycle-electrochemical carboxylation), sequential aryl/vinyl radical cyclization-electrochemical carboxylation, sacrificial anode-free electrochemical carboxylation, and the use of supercritical carbon dioxide both as a reaction media and a reagent were also developed. In this personal account, our efforts in and results of electrochemical fixation of carbon dioxide to organic compounds with carbon-carbon bond forming reactions yielding novel and useful carboxylic acids are introduced along with their applications and some new results.

Organic chemistry: an acid-base approach

A DFT investigation of substituent effects on carbon dioxide fixation: by a low-coordinate cobalt (I) complex

Efficient Fixation of Carbon Dioxide by Electrolysis — Facile Synthesis of Useful Carboxylic Acids —

Event Abstract Back to Event DFT investigation of Methane (CH4) and Carbon Dioxide (CO2) to Acetic Acid Bruce M. Prince1* 1 Texas Southern University, United States Conversion of unactivated methane gas (CH4) and carbon dioxide (CO2) to form carboxylic acids represents an important industrial process that improved the drawbacks that generate significant waste via traditional carbonylation of methanol. Acetic acid is an important precursor in the production of various synthetic fibers, polyethylene terephthalate: soft drink bottles, cellulose acetate: photographic film, polyvinyl acetate: wood glue, vinegar: food industry, etc. The research herein seeks to avoid the production of greenhouse gases, and focuses on homogenous catalysis by transition metals for the production of carboxylic acids by pathways that involve metal-mediated CO2 fixation, C-C insertion, oxidative hydrogen migration or oxidative addition of aliphatic C—H bonds. An improved catalyst should avoid side reactions such as formyl ester species. The metal-mediated fixation of carbon dioxide and methane gas to produce acetic acid is depicted in Scheme 1. This presentation provides the investigated results of modeling the potential energy surface (PES) of CO2 plus CH4, the uncomplicated process focused on the impact of the supporting ligand (Ln) upon the kinetics and thermodynamics of direct carboxylation of methane gas. Acknowledgements This work was supported in part by Texas Southern University (TSU) HPC (http://hpcc.tsu.edu/; Grant PHY-1126251). TSU department of Chemistry and the Center for Catalysis Computational Research (3CR), and by the NSF Houston-Louis Stokes Alliance for Minority Participation (LSAMP) (TSU) HRD-1407736. References (1) Prince, B. M. A DFT Investigation of Substituent Effects on Carbon Dioxide Fixation: By a Low-Coordinate Cobalt (I) Complex Computational and Theoretical Chemistry 2017 1122, 1-8. Keywords: CO2 fixation, Acetic Acid, C-H activation, greenhouse gases, Methane, CH4, Acetate complex, CO2 sequestering Conference: National Organization for the Professional Advancement of Black Chemists and Chemical Engineers (NOBCChE) 45th Annual Conference , Orlando, Florida, United States, 17 Sep - 20 Sep, 2018. Presentation Type: Oral Presentation Topic: Inorganic and Materials Chemistry Citation: Prince BM (2019). DFT investigation of Methane (CH4) and Carbon Dioxide (CO2) to Acetic Acid. Front. Chem. Conference Abstract: National Organization for the Professional Advancement of Black Chemists and Chemical Engineers (NOBCChE) 45th Annual Conference . doi: 10.3389/conf.fchem.2018.01.00064 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 18 Oct 2018; Published Online: 17 Jan 2019. * Correspondence: Dr. Bruce M Prince, Texas Southern University, Houston, United States, bruce.prince@tsu.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Bruce M Prince Google Bruce M Prince Google Scholar Bruce M Prince PubMed Bruce M Prince Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

The recent literature concerning the fixation of carbon dioxide with transition metal complexes is surveyed. Carbon dioxide forms adducts with various transition metal complexes and reacts with transition metal complexes having metal-carbon, hydrogen, oxygen and nitrogen bonds to give its insertion products into these bonds. Based on the information accumulated concerning the reactivity of CO2 with transition metal complexes, several feasible prospects utilizing carbon dioxide as one of the cheapest carbon resources are presented and critically discussed.

Photochemical fixation of supercritical carbon dioxide: the production of a carboxylic acid from a polyaromatic hydrocarbon

Carbon Dioxide as Chemical Feedstock

Decarboxylation and decarbonylation are important reactions in synthetic organic chemistry, transforming readily available carboxylic acids and their derivatives into various products through loss of carbon dioxide or carbon monoxide. In the past few decades, palladium-catalyzed decarboxylative and decarbonylative reactions experienced tremendous growth due to the excellent catalytic activity of palladium. Development of new reactions in this category for fine and commodity chemical synthesis continues to draw attention from the chemistry community. The Stoltz laboratory has established a palladium-catalyzed enantioselective decarboxylative allylic alkylation of β-keto esters for the synthesis of α-quaternary ketones since 2005. Recently, we extended this chemistry to lactams due to the ubiquity and importance of nitrogen-containing heterocycles. A wide variety of α-quaternary and tetrasubstituted α-tertiary lactams were obtained in excellent yields and exceptional enantioselectivities using our palladium-catalyzed decarboxylative allylic alkylation chemistry. Enantioenriched α-quaternary carbonyl compounds are versatile building blocks that can be further elaborated to intercept synthetic intermediates en route to many classical natural products. Thus our chemistry enables catalytic asymmetric formal synthesis of these complex molecules. In addition to fine chemicals, we became interested in commodity chemical synthesis using renewable feedstocks. In collaboration with the Grubbs group, we developed a palladium-catalyzed decarbonylative dehydration reaction that converts abundant and inexpensive fatty acids into value-added linear alpha olefins. The chemistry proceeds under relatively mild conditions, requires very low catalyst loading, tolerates a variety of functional groups, and is easily performed on a large scale. An additional advantage of this chemistry is that it provides access to expensive odd-numbered alpha olefins. Finally, combining features of both projects, we applied a small-scale decarbonylative dehydration reaction to the synthesis of α-vinyl carbonyl compounds. Direct α-vinylation is challenging, and asymmetric vinylations are rare. Taking advantage of our decarbonylative dehydration chemistry, we were able to transform enantioenriched δ-oxocarboxylic acids into quaternary α-vinyl carbonyl compounds in good yields with complete retention of stereochemistry. Our explorations culminated in the catalytic enantioselective total synthesis of (–)-aspewentin B, a terpenoid natural product featuring a quaternary α-vinyl ketone. Both decarboxylative and decarbonylative chemistries found application in the late stage of the total synthesis.

Biomass derived oils, made from decomposition and conversion of biomass feedstocks, are proposed as alternative sustainable fuels and potential precursors to valuable chemicals. Bio-oils are produced using different approaches including hydrothermal liquefaction and fast pyrolysis of biomass feedstocks. The composition of bio-oils varies depending on the biomass source as well as on the production method. Bio-oils also contain various functional groups including carboxyl, ketone, aldehyde, phenol etc. Among the functional groups, compounds containing oxygenated species such as carboxyl, phenol and ketone groups can be particularly corrosive to metallic and polymeric materials used for transportation, production, and storage of bio-oils. Formic and acetic acids are some of the most prevalent carboxylic acids present in fast-pyrolysis bio-oils and pose a concern for corrosion of metal alloys. In the present study, we varied the amounts of carboxylic acids in a forest residue fast pyrolysis bio-oil to assess their effects on corrosion of type 410 stainless steel (410SS). To study the effect of formic and acetic acids on corrosion in bio-oils, we exposed 410SS specimens in FR3 (forest residue, fast pyrolysis bio-oil) in short term (48 hour), mild temperature (50 °C) exposures. 410SS specimens were polished, weighed and exposed to fast pyrolysis bio-oil (FR3) with baseline modified total acid number (AMTAN) value of 50.1 mg of KOH per gram of bio-oil. Using a piece of Teflon string, specimens were suspended in approximately 25 g of bio-oil at 50 °C for 48 hours. The oil samples were then spiked with either formic or acetic acids. Capillary electrophoresis was used to quantify formic and acetic acids present in the bio-oil. The area under the curves were determined and correlated to concentration of each specie using standards. Electrochemical Impedance Spectroscopy (EIS) was also performed to investigate corrosion behavior of 410SS in FR3 bio-oil at room temperature. A miniature glass cell & Luggin capillary to minimize ohmic drop within the bio-oil phase was utilized. Reference mercury sulfate electrode and platinum mesh counter electrode were used for EIS measurements.The results of short-term (48 hour, 50°C) exposures of 410SS coupons in bio-oils with addition of small carboxylic acids are shown in Figure 1. Mass change plot vs the concentration of formic acid is shown in the left graph. We observed linear increase in mass loss of 410SS with increasing formic acid concentration in the bio-oil. This is expected given our previous results that showed corrosivity of formic acid towards low chromium alloys. Iron formate was the main corrosion product that formed on the surface. However, acetic acid shows the opposite effect on mass change data as shown in the graph on the right in Figure 1. Increasing addition of acetic acid resulted in decreased mass loss. This result is intriguing because acetic acid unexpectedly behaves as a corrosion inhibitor. We are currently performing more experiments to study this effect and to understand the reason for seemingly inhibitory effect of acetic acid on corrosion of 410 stainless steel. Mass changes and cross-sectional examination of post-exposure SS410 specimens, using scanning electron microscopy equipped with energy dispersive x-ray spectroscopy, will also be presented. Impedance data from EIS measurements were analyzed as another means to assess corrosion performance of SS410 in the bio-oil and used for comprehensive corrosion assessment along with other results. Funding provided by DOE Bioenergy Technologies Office. Figure 1

Abstract: Electrochemical reduction of organic compounds in the presence of carbon dioxide results in the fixation of carbon dioxide into the substrates with carbon-carbon bond forming reaction to yield the corresponding carboxylic acids. The reaction is called “electrochemical carboxylation” or “electrocarboxylation”. Various kinds of carboxylic acids have been synthesized using carbon dioxide as a carboxyl group source by electrochemical carboxylation. In this mini-review, several representative kinds of carboxylic acids synthesized from carbon dioxide by electrochemical carboxylation are briefly summarized/introduced, comparing past and latest.